全文获取类型
收费全文 | 10797篇 |
免费 | 1071篇 |
国内免费 | 680篇 |
专业分类
化学 | 650篇 |
晶体学 | 7篇 |
力学 | 594篇 |
综合类 | 286篇 |
数学 | 8863篇 |
物理学 | 2148篇 |
出版年
2024年 | 29篇 |
2023年 | 138篇 |
2022年 | 200篇 |
2021年 | 243篇 |
2020年 | 354篇 |
2019年 | 372篇 |
2018年 | 335篇 |
2017年 | 356篇 |
2016年 | 299篇 |
2015年 | 229篇 |
2014年 | 370篇 |
2013年 | 836篇 |
2012年 | 425篇 |
2011年 | 535篇 |
2010年 | 494篇 |
2009年 | 685篇 |
2008年 | 709篇 |
2007年 | 595篇 |
2006年 | 636篇 |
2005年 | 472篇 |
2004年 | 435篇 |
2003年 | 438篇 |
2002年 | 447篇 |
2001年 | 405篇 |
2000年 | 404篇 |
1999年 | 333篇 |
1998年 | 298篇 |
1997年 | 206篇 |
1996年 | 162篇 |
1995年 | 121篇 |
1994年 | 130篇 |
1993年 | 95篇 |
1992年 | 92篇 |
1991年 | 85篇 |
1990年 | 68篇 |
1989年 | 63篇 |
1988年 | 63篇 |
1987年 | 48篇 |
1986年 | 32篇 |
1985年 | 49篇 |
1984年 | 64篇 |
1983年 | 27篇 |
1982年 | 33篇 |
1981年 | 33篇 |
1980年 | 18篇 |
1979年 | 16篇 |
1978年 | 16篇 |
1977年 | 13篇 |
1976年 | 12篇 |
1975年 | 7篇 |
排序方式: 共有10000条查询结果,搜索用时 31 毫秒
101.
Zhang Shenggui Sun Hao Li Xueliang .Dept.of Appl. Math. Northwestern Polytechnical Univ. Xi''''an China. .Center of Combinatorics Nankai Univ. Tianjin China. 《高校应用数学学报(英文版)》2002,(3)
§ 1 IntroductionAll graphsconsidered in this paperare finite undirected ones withoutloops ormultipleedges.Our terminology and notation are standard exceptas indicated.A good reference forany undefined terms is[1 ] .Let G be a graph with vertex set V( G) and edge set E( G) .The density of G is definedbyd( G) =ε( G)ν( G) ,whereν( G) andε( G) denote| V( G) | and| E( G) | ,respectively.G is said to be balanced iffor each subgraph H of G we have d( H )≤ d( G) ,where V( H ) is assum… 相似文献
102.
Solomon Fekade Mulugeta Bekele 《The European Physical Journal B - Condensed Matter and Complex Systems》2002,26(3):369-374
We analyze the relaxation behavior of a bistable system when the background temperature profile is inhomogeneous due to the
presence of a localized hot region (blowtorch) on one side of the potential barrier. Since the diffusion equation for inhomogeneous
medium is model-dependent, we consider two physical models to study the kinetics of such system. Using a conventional stochastic
method, we obtain the escape and equilibration rates of the system for the two physical models. For both models, we find that
the hot region enhances the escape rate from the well where it is placed while it retards the escape rate from the other well. However, the value of the escape rate from the well where the hot region is placed differs
for the two models while that of the escape rate from the other well is identical for both. This work, for the first time,
gives a detailed report of the similarities and differences of the escape rates and, hence, exposes the common and distinct
features of the two known physical models in determining the way the bistable system relaxes.
Received 25 September 2001 相似文献
103.
1989年发表的Bager第五图,包含关于三角形元素的35个二次规范画数之间的51个不等式通过细致的分析,本文给出了其中遗漏的12个基本不等式 相似文献
104.
侯旻 《新疆大学学报(理工版)》1991,(1)
本文比较了循环图类{c_p(n_1,…,n_p)}和{c-p(n_1…,n_p,p/α)}的直径下界。对于p和α满足一定条件的循环图类{c_p(n_1,n_2,p/α)},本文给出了达到或几乎达到此图类直径下界的一类几乎最优循环图{c_p(m,m+1,p/α)}。 相似文献
105.
Youssef Saab 《Journal of Heuristics》1997,3(3):207-224
A heuristic optimization methodology, Dynamic Contraction (DC), is introduced as an approach for solving a wide variety of hard combinatorial problems. Contraction is an operation that maps an instance of a problem to a smaller instance of the same problem. DC is an iterative improvement strategy that relies on contraction as a mechanism for escaping local minima. As a byproduct of contraction, efficiency is improved due to a reduction of problem size. Effectiveness of DC is shown through simple applications to two classical combinatorial problems: The graph bisection problem and the traveling salesman problem. 相似文献
106.
The theory of nonequilibrium potentials or quasipotentials is a physically motivated approach to small random perturbations of dynamical systems, leading to exponential estimates of invariant probabilities and mean first exit times. In the present article we develop the mathematical foundation of this theory for discrete-time systems, following and extending the work of Freidlin and Wentzell, and Kifer. We discuss strategies for calculating and estimating quasipotentials and show their application to one-dimensionalS-unimodal maps. The method proves to be especially suited for describing the noise scaling behavior of invariant probabilities, e.g., for the map occurring as the limit of the Feigenbaum period-doubling sequence. We show that the method allows statements about the scaling behavior in the case of localized noise, too, which does not originally lie within the scope of the quasipotential formalism. 相似文献
107.
We address in this paper the problem of finding an optimal strategy for dealing with bottleneck machines and bottleneck parts in the cell formation process in group technology. Three types of economic decisions are considered: subcontracting, machine duplication and intercell moves. The problem is formulated as a minimum weighted node covering problem in a hypergraph, and we show that it can be solved in polynomial time by finding a maximum weighted stable set in a bipartite graph. We extend this result to cellular manufacturing systems in which the sequence of operations of each part is known in advance. 相似文献
108.
In the core of the seminal Graph Minor Theory of Robertson and Seymour lies a powerful theorem capturing the ``rough' structure
of graphs excluding a fixed minor. This result was used to prove Wagner's Conjecture that finite graphs are well-quasi-ordered
under the graph minor relation. Recently, a number of beautiful results that use this structural result have appeared. Some
of these along with some other recent advances on graph minors are surveyed.
Research partly supported by Japan Society for the Promotion of Science, Grant-in-Aid for Scientific Research, Grant number
16740044, by Sumitomo Foundation, by C & C Foundation and by Inoue Research Award for Young Scientists
Supported in part by the Research Grant P1–0297 and by the CRC program
On leave from: IMFM & FMF, Department of Mathematics, University of Ljubljana, Ljubljana, Slovenia 相似文献
109.
采用无规相近似(RPA)方法,用空心图作为试探波函数,利用Feymann?Hellman定理计算七阶2?+?1维SU(2?)格点规范场的胶球质量,在弱耦合区1/g2?=1.0?–?1.8胶球质量表现出良好的标度行为,基本趋于常数(m/e2?≈1.2?0±0?.0?1)?. 相似文献
110.
既不离散也不连续的随机变量 总被引:2,自引:1,他引:1
讨论了既不离散也不连续的随机变量 ,并纠正了有关文献中关于连续型随机变量定义中的错误 . 相似文献